Making a tube preamp out of this??

[comfortably_numb]

I've been looking at various tube preamp schematics, including the Real McTube II and the Tube Driver.  I'm curious however, if anyone would be able to configure the schematic for the AX84 "P1" to use only the preamp.  I'd like to keep the tone stack along with the master volume.  What I'm wondering is if there is an efficient way to power these tubes with maybe a different transformer, since I won't be using the output stage.  Shouldn't I need a bit less power?  Can someone point me in the right direction concerning that?

Also, does anyone have any other tube preamps they would recommend?  I'm not looking for overdrive so much as a tube stage to warm up my solidstate setup.  I'd like a clean stage that could be overdriven with a booster/distortion.  A two channel preamp could be cool too.  Okay...that's all.  Here is the URL for the P1 schematic:  http://annex.ax84.com/media/ax84_m311.pdf

Thanks

[jrc4558]

I would say, a standard Princeton preamp will do nicely. Especially at lower plate voltages, like those that you will get with 269EX.
http://www.ampwares.com/ffg/schem/princeton_5f2_schem.gif

[andy123]

Hi,

Did you consider a Hot box?  or maybe something like the SD FX03?


Andy

[scaesic]

hi!

i'm also intrested in seperating pre-amp and power-amp sections of amp scematics and marrying the ones i like together, but i'm not entirely sure if it's as easy as fitting two lego peices together. We need INFO!

more-over, how easy is it to increase the headroom of a poweramp/preamp? i was thinking about trying to increase the power-amp part of the p1 so i could have an A-class amp with a bit more headroom to play cleaner at louder volumes.

[d95err]

more-over, how easy is it to increase the headroom of a poweramp/preamp? i was thinking about trying to increase the power-amp part of the p1 so i could have an A-class amp with a bit more headroom to play cleaner at louder volumes.

To increase headroom in a poweramp, you need higher voltages, more tubes or higer output tubes. Messing with the phase splitter could also get some more headroom, but since the P1 is single ended it doesn't have a phase splitter. To get significantly more power, it's probably better to build a different amp, e.g. the AX84 California Dreamer.

[jrc4558]

hi!

i'm also intrested in seperating pre-amp and power-amp sections of amp scematics and marrying the ones i like together, but i'm not entirely sure if it's as easy as fitting two lego peices together. We need INFO!

more-over, how easy is it to increase the headroom of a poweramp/preamp? i was thinking about trying to increase the power-amp part of the p1 so i could have an A-class amp with a bit more headroom to play cleaner at louder volumes.

Separating is pretty simple. Building them separately is simple as well. The only "hard" part is getting expensive power transformers for every build of yours.

Increasing the headroom of preamp is easy. You can do so by increasing the plate voltages (smaller decoupling resistors, or tapping power off of the B+ supply directly, through 10K/22цF network)

Increasing the headroom of a power amp usually involves the same higher plate voltages, however, those are harder to achieve because output tubes get their power almost directly from the first power supply decoupling/filtering capacitor. Thus, in order to rise the plate voltages you need a different power transformer, but beware. Ecvery tube has a limit for how high you can go on plate voltages.
sometimes, and especially if you want a SE design, using two tubes in parallel helps. in thiscase you need to make sure that your power transformer can produce the necessary current.

Usual warnings about high voltage apply.

good luck!

[comfortably_numb]

Maybe I should join an amp forum for this, but can anyone give me some insight into the transformer aspect of schematics?  Are the different parts coming off of it different outputs that are inherent in the transformer design, or is there something I need to do to make those various supply lines?  I'm just a bit confused.  Is there a good preamp that I could use that runs off of just 9V?  I'd like some good clean tones, and possibly a switchable overdrive channel.  Also, as before, a tone stack (low, mid, high).

I'll be checking out the hotbox, and the SD fx03.  Also, what is 269ex?  A transformer?

[jrc4558]

honestly, build a peppermill, swap some capacitors there, an you will get it "tubey-er". Dont run tubes at 9VDC. Sounds just like another FET, just a very high Vgoff.

[comfortably_numb]

well I took a look at the peppermill.  Looks pretty interesting.  Also, the fetzer valve and the professor tweed may have a nice effect on my setup. 

But, I'm still interested in putting a big clean tube stage in front of my amp (or straight into the power amp section).  Can anyone help me understand those transformers or send me in the right direction?

I've heard that people don't really like the McTube...  Is that just for overdrive?  Would it make a nice clean stage?  And is it loud enough to add a fender tone stack?

[bancika]

269EX is Hammond transformer. You can use two back to back transformers instead. I'm about to start hotbox with few switchable mods when parts come